1. Field of the Invention
The present invention relates to a tape cassette having a pair of reels, on which a magnetic tape is wound, in a cassette holder, and particularly, to a reel-locking mechanism to lock and unlock a pair of reels by controlling their rotation.
2. Description of the Related Art
A conventional tape cassette used for a device such as a video tape recorder (hereafter, called as VTR), a VTR integrated with a camera, or the like is generally provided with a reel-locking mechanism to control (lock and unlock) rotation of a pair of reels, on which a magnetic tape is wound, when the device is not used. A configurations, shown, for example, in FIG. 13 to 16 has been well known for the reel-locking mechanism of such a tape cassette.
FIG. 13 shows an exploded view of a conventional tape cassette 1 for recording and reproducing. It comprises a cassette housing 2 having a upper shell 2a and a lower shell 2b which are laid superposed one another; a pair of reels 3a, 3b accommodated in the cassette housing 2; a magnetic tape 4 which is fixed at both ends to both the reels 3a, 3b, and wound properly; a reel-locking mechanism 9 to control the rotation of the pair of reel 3a, 3b; and so on. The lower shell 2b of the cassette housing 2 is provided with two hub holes 5a, 5b, in which the pair of supply side reel 3a and take-up side reel 3b are loosely fitted, and on which the reels are rotatably supported.
In addition, the front portion of the cassette housing 2 is provided with a loading opening portion 6 into which the guide pin of the loading mechanism (not shown) and so on enter, and tap inserting holes 7a, 7b open to the outside at both outer sides of the opening portion 6. Guiding portions 8a, 8b to guide the magnetic tape 4 are also installed inside the holes 7a, 7b, respectively. Thus, the tape 4 drawn out from the supply side reel 3a is guided through the tape inserting hole 7a on one outer side to the outside of the cassette housing 2 to cross the loading opening portion 6. And, the tape 4 enters through the tape inserting hole 7b on the other outer side, again, into the cassette housing 2 to be wound around the take-up side reel 3b. 
The rear portion of the cassette housing 2 is provided with the reel-locking mechanism 9 disposed opposing almost the midway portion between a pair of reels 3a, 3b. The reel-locking mechanism 9 prevents the slack in the magnetic tape 4 by locking both reels 3a, 3b, when the tape cassette 1 is not used, to stop the rotation of the reels. The reel-locking mechanism 9 comprises a reel-locking main body 10 slidably supported by the lower shell 2b; a pair of reel-locking pieces 11, 12 swingablly provided in the reel-locking main body 10; a spring for sliding 13 to urge the reel-locking main body 10 toward the reels 3a, 3b; and a reel-locking spring 14 to impart spring force to a pair of reel-locking pieces 11, 12.
The reel-locking main body 10 is provided with a pair of axis portions 10a, 10b; the bottom surface with guide grooves 10c; and the top surface with guide bumps 10d. A pair of reel-locking pieces 11, 12 are swingably supported on the pair of axis portions 10a, 10b of the reel-locking main body 10, as shown in FIG. 14. The reel-locking pieces 11, 12 have pawl portions 11a, 12a, respectively and are biased to be always open to the outside by spring force of the reel-locking spring 14.
The reel-locking spring 14 has a configuration where a pair of torsion springs are connected to compose one integrated body. The reel-locking spring 14 has a pair of coil portions 14a, 14b disposed at the right and left sides; a U-shaped connection portion 14c connecting one end of the coil portions 14a, 14b; and spring, pieces 14d, 14e provided at the other end of the respective coil portions 14a, 14b. A pair of coil portions 14a, 14b of the reel-locking spring 14 is loosely engaged with the outside of a pair of axis portions 10a, 10b with which the pair of reel-locking pieces 11, 12 are engaged.
Rotating force in the reel-locking direction is given to the respective reel-locking pieces 11, 12 by engagingly stopping spring pieces 14d, 14e at both right and left ends of the reel-locking spring 14 into the pair of reel-locking pieces 11, 12. At this time, the connection portion 14c of the reel-locking spring 14 is put on the upper surface of the reel-locking main body 10. Elasticity is imparted to the spring pieces 14d, 14e at both ends by connecting right and left coil portions 14a, 14b at the connection portion 14c. Thereby, swing force is given to the pair of reel-locking pieces 11, 12.
The reel-locking mechanism 9 with such a configuration is installed in a predetermined location of the cassette housing 2 as shown in FIG. 15 to control (lock and unlock) rotation of the pair of reels 3a, 3b. The reel-locking main body 10 of the reel-locking mechanism 9 is guided by main body guide ribs 15a, 15b provided in the upper and lower shells 2a, 2b, as shown in FIG. 16, and movably supported in the front to rear direction (perpendicular to the direction connecting the centers of the pair of reels 3a, 3b) of the tape cassette 1. That is, the main body guide rib 15b of the lower shell 2b is engaged with a guide groove 10c of the reel-locking main body 10. The main body guide rib 15a of the upper shell 2a is engaged with the guide projected portion 10d. And, the reel-locking main body 10 is always urged forward by the coil spring 13 one end of which sits in the rear surface of the cassette housing 2.
In addition, on both sides in the left to right direction (direction perpendicular to the front to rear direction) of the main guide ribs 15a, 15b of the cassette 2 are provided a pair of right and left locking piece guide ribs 16, 16 extending in the front to rear direction at a predetermined space. Cam portions 16a, 16a whose tips are made to fan out one another are provided in the inside of the pair of locking pieces guide ribs 16, 16. Contacting portions 11b, 12b of the pair of reel-locking pieces 11,12 urged by spring force of the reel-locking spring 14 come in contact with the cam portions 16a, 16a. 
In addition, as shown in FIG. 16, in order to hold the inside of the cassette housing 2 to the light, the upper shell 2a is provided with a window portion 17 formed from colorless transparent plastic material. The upper shell 2a with such the window portion 17 has been generally manufactured by injection molding using a double color die. Such a die has been usually provided with a partition in order to prevent colored opaque resin composing the main body portion of the upper shell 2a from entering into the window portion 17 during manufacturing. The partition forms a concave portion 17a in the upper shell 2a. 
The operation of the reel-locking mechanism having the above configuration will be described below. FIG. 15 describes the reel-locking mechanism 9, and shows a state that the tape cassette 1 is loaded to a cassette deck (not shown). In this case, when the tape cassette 1 is loaded to the cassette deck, and a reel-unlocking member 18 (See FIG. 16) provided in the cassette deck enters into the reel-locking main body 10. As a result, the reel-locking main body 10 is moved backward (the rear side of the cassette deck 1) against spring force of the coil spring 13.
Therewith, the pair of reel-locking pieces 11, 12 are respectively guided by the cam portions 16a of the locking piece guide ribs 16 to be swung toward the reel-locking main body 10 against the spring force of the reel-locking spring 14. Thereby, the pawl portions 11a, 12a of the pair of reel-locking pieces 11, 12 are respectively disengaged with the engaging teeth 3c, 3c of the pair of reels 3a, 3b with the result that the locking of the pair of reels 3a, 3b is released. As a result, it becomes possible for both the reels to rotate, and the magnetic tape 4 is wound from the one reel to the other reel by the rotation of a pair of reel bases (not shown) installed to both the reels 3a, 3a. 
On the other hand, though not illustrated, when the tape cassette 1 is not used (a state of being taken out from the cassette deck), the reel-locking main body 10 is urged forward by spring force of the sliding spring 13. Concurrently, being urged by spring force of the reel-locking spring 14, the pawl portions 11a, 12a of the pair of reel-locking pieces 11, 12 are opened outward. And, the pair of pawl portions 11a, 12a are engagingly stopped by the engaging teeth 3c, 3c of the pair of the reels 3a, 3b with the result that the pair of reels 3a, 3b is placed in a state of being locked. As a result, the rotation of both reels 3a, 3b is prevented, thereby generating no slack in the magnetic tape 4 in the circumstances.
However, the upper shell 2a of the above conventional tape cassette has been formed by two colors molding. When manufacturing the upper shell 2a, the concave portion 17a is provided to form a partition in order to prevent resin composing the main body from entering into the window portion 17. The reel-locking spring 14 of the reel-locking mechanism 9 is formed near the concave portion 17a. Thereby, at a time of the tape cassette 1 being taken out of the cassette deck, when the reel-locking main body 10 is moved forward by spring force of the coil spring 13, the connection portion 14c of the reel-locking spring 14 tends to be easily caught in the concave portion 17a. 
As a consequence, when the connection portion 14c of the reel-locking spring 14 gets caught in the concave portion 17a to come to a standstill, since the reel-locking main body 10 to which the reel-locking spring 14 is fit is unable to move forward to the predetermined position, it becomes impossible for the pawl portions 11a, 12a of the pair of reel-locking pieces 11, 12 to respectively engage with the engaging teeth 3c, 3c of the pair of reels 3a, 3b, and rotation of both reels 3a, 3b comes to be unable to be stopped. As a result, since the pair of reels 3a, 3b are kept in a state capable of rotating, when vibration and impact by falling are applied to the tape cassette 1, there is a possibility that too much slack in the tape is generated by free rotation of the pair of reels 3a, 3b, for example. Consequently, there has been a problem that too much slack in the magnetic tape 4 of the tape cassette 1 causes a fear of the magnetic tape 4 being entangled at the time of loading the magnetic tape 4 to the cassette deck 1.
The present invention is made to solve the above problem, and an object of the invention is to provide a tape cassette which ensures smooth operation of a reel-locking mechanism, and reliable locking and unlocking of a pair of reels.
In order to solve the above problem or the like and achieve the above object, the present invention is a tape cassette comprising; a pair of reels which are accommodated between an upper shell and a lower shell superposed each other with a magnetic tape in a state of being wound on the reels, and have engaging teeth respectively; a reel-locking main body which is movable forward and backward relative to the pair of reels, and supported by the lower shell; a pair of reel-locking pieces swingably supported on the reel-locking main body, and having pawl portions at the tip respectively; and a reel-locking spring having a pair of coil portions loosely fit to swinging center portions of pair of reel-locking pieces, and urging the pair of pawl portions toward the pair of reels, respectively; the cassette performing locking and unlocking of the pair of reels through engagement and disengagement of the pair of pawl portions with/from the pair of engaging teeth by movement of reel-locking main body, characterized in that a connection portion connecting the pair of coil portions of the reel-locking spring is bent toward the reel-locking main body to press the reel-locking main body by spring force of the connection portions.
By the above configuration of the present invention, the connection portions connecting the pair of coil portions of the reel-locking spring is bent toward the reel-locking main body to press the reel-locking main body by the spring force of the connection portion. Thereby, when the tape cassette is taken out of the cassette deck, it is possible to do away with the fear of the connection portion of the reel-locking spring of the reel-locking mechanism being caught in the concave portion of the upper shell and also, it is possible to ensure smooth and reliable reel-locking operation, and there may be no slack in the magnetic tape.